Coordicide: Would using public key encryption as a mechanism for node identity impact Iota's quantum resistance?

Question

per the white paper

In order to identify nodes, it is necessary to introduce global node identities. Tothis end, we envision using common public key cryptography to sign certain dataand to link it to its issuing node in a tamper proof way. Additionally, we requirethat the issuing node adds its public key to every signed message. This way,every node can verify the authenticity of the issuing node without the need forsome form of global database of IDs and keys

Wouldn't quantum computing allow a malicious actor to potentially spoof the signatures of many honest nodes as an attempted attack? How would the network respond?

Answer 1

According to the document:

In contrast to any data stored in the Tangle, the communication layer, therefore, does not necessarily require the use of post-quantum cryptography right now, but it can be swapped when quantum attacks become more imminent in the future.

In case of quantum computer attacks become feasible, a dishonest node that has the power to partition the network, could double spend and sign different, conflicting messages "from" many nodes to different other nodes (in the two partitions of the network), therefore making part of the network to reject a transaction that is accepted in the other part.

However, when the networks rejoin, it will still eventually result in a consensus that both double spends are invalid. Perhaps one of the receivers has already believed before that his transaction was legitimately accepted (because the nodes believed that) and already sent his valuable goods to the attacker.

I think the whitepaper promotes the idea that it will swap this consensus signing algorithm with a quantum-resistant one once quantum attacks get more feasible and, therefore, quantum resistant cryptography gets better. Unlike the signatures used by your IOTA addresses, such an algorithm switch has no impact on your balance and you don't have to transition your money. The signatures are only used for the consensus protocol.